Angered by a resounding defeat Wednesday of proposed gun control legislation that grew out of the Sandy Hook Elementary School massacre, President Barack Obama stood outside the White House with parents of murdered Newtown first-graders and vowed: "This effort is not over."

"All in all, this was a pretty shameful day for Washington," Obama said after the Democratic-controlled Senate failed to approve a measure calling for expanded background checks in gun purchases. The vote was 54-46 in favor, but that was six shy of the 60 votes needed to overturn a Republican filibuster.

Speaking with a pointed intensity, Obama blamed Wednesday's defeat on the national gun lobby's alleged lies and incumbent senators' political fears – which, he said, overcame overwhelming support by 90 percent of Americans for compromise legislation that represented "progress … moderation … and common sense."

"Instead of supporting this compromise, the gun lobby and its allies willfully lied about the bill. They claimed that it would create some sort of big brother gun registry – even though the bill did the opposite" and "in fact, outlawed any registry," Obama said.

Senators began to worry that a "vocal minority of gun owners would come after them in future elections," Obama said. "They worried that the gun lobby would spend a lot of money and paint them as anti-Second Amendment. … And so they caved to the pressure, and they started looking an excuse – any excuse – to vote 'no.' "

"The fact is, most of these senators could not offer any good reason why we wouldn't want to make it harder for criminals, and those with severe mental illnesses, to buy a gun," Obama said. "There were no coherent arguments as to why we wouldn't do this. It came down to politics."

A compromise measure fashioned by Sen. Pat Toomey, R-Pa., and Sen. Joe Manchin, D-W.Va., would have required a background check on all commercial sales – expanding current federal law that only applies to firearms retailers to include now-exempt online transactions and gun shows. Private transfers, however, would have remained untouched – a compromise that stopped short of a universal background check requirement.

"Expanded background checks wouldn't have saved our loved ones, but still we came to support the bipartisan proposal from two senators, both with A ratings from the NRA," said Sandy Hook parent Mark Barden, who introduced Obama at the White House.

"It's a proposal that will save lives without interfering with the rights of responsible, law-abiding gun owners," Barden said. "We'll return home now, disappointed but not defeated. We return home with the determination that change will happen — maybe not today, but it will happen. It will happen soon."

Wednesday's rejection in Washington came two weeks after Connecticut approved gun legislation that requires universal background checks, bans large capacity magazines and expands a ban on assault weapons.

The Toomey-Manchin compromise rejected Wednesday was far weaker than the federal bans on assault weapons and high capacity ammunition magazines sought by Obama and other gun control advocates in the four months since Dec. 14. That was the day 20 children and six women were shot to death by Adam Lanza, 20, with a semiautomatic Bushmaster AR-15 rifle. Lanza killed himself when police arrived at the school.

The depths of gun control supporters' deflation Wednesday showed in Obama's blunt concession that there's no hope in the Republican-controlled House of Representatives. "You can have something that 90 percent of Americans support and you can't get it through the Senate or the House of Representatives," he said.

The president said those who blocked the legislation are outnumbered by supporters of the defeated measure. But, he added, "they're better organized, they're bettered financed, they've been at it longer."

NRA Executive Director Chris W. Cox said Wednesday that the "misguided" proposal rejected by the Senate "would have criminalized certain private transfers of firearms between honest citizens, requiring lifelong friends, neighbors and some family members to get federal government permission to exercise a fundamental right or face prosecution. As we have noted previously, expanding background checks, at gun shows or elsewhere, will not reduce violent crime or keep our kids safe in their schools."

He said that the NRA "will continue to work with Republicans and Democrats who are committed to protecting our children in schools, prosecuting violent criminals to the fullest extent of the law, and fixing our broken mental health system."

Obama said that he's heard some say that blocking the legislation was a "victory."

"My question is, a victory for who? A victory for what? All that happened today was the preservation of the loophole that lets dangerous criminals buy guns without a background check. That doesn't make our kids safer." With such a strong majority of Americans supporting the compromise, he said it "begs the question: Who are we here to represent?"

But Obama said: "I see this as just round 1."

He and other advocates said late Wednesday that they want to begin taking the names of those who vote against popular gun control legislation and turn them out of office in future elections.

"To change Washington, you the American people are going to have to sustain some passion about this. And when necessary you've got to send the right people to Washington," Obama said. "And that requires strength, and it requires persistence – and that's the one thing that these families should have inspired in all of us. I still don't know they have even able to muster up the strength to do what they've been doing over the last several weeks, the last several months."

At the White House, Obama stood with Vice President Joe Biden and former Arizona congresswoman Gabrielle Giffords, who survived a shooting two years ago. They were surrounded by the parents from Sandy Hook elementary who have been lobbying senators in private meetings for the last week.

Barden, whose youngest child, Daniel, was killed Dec. 14, said that when he and other parents arrived in Washington, D.C., senators were prepared to filibuster, and the fact that gun legislation was brought to a vote is a success.

"We are in it for the long haul," Barden said Wednesday night. "I think the attitudes of the vast majority of Americans are there."

The background check provision was one of seven amendments to a gun control bill that the Senate rejected Wednesday for lack of the required 60 votes; the overall bill hasn't come to a vote.

One of the amendments, introduced by Sen. Richard Blumenthal, D-Conn., would have banned large capacity ammunition magazines such as the 30-round magazines used by Lanza at Newtown. The vote was 54-46 against Blumenthal's measure.

The Senate will continue voting on Thursday, but the failure of the significant measures spelled overall defeat for gun control advocates.

Blumenthal and his fellow Connecticut senator, Democrat Chris Murphy, told reporters in an evening conference call that they would keep fighting.

"Today was heartbreaking, one of the saddest and shocking days of my life in public service, maybe my whole career," Blumenthal said. "The hardest part of the day was really deciding how to explain to families that … 54 senators could vote for a measure and yet have it fail. … What will change is the American people telling their senators they are aghast and outraged at the result."

Murphy said: "I don't know what's worse, that the NRA lied or that they got away with it," echoing the president.

Murphy was one of the advocates who vocally wanted to "demand a vote" for Newtown, in order to get senators on the record as supporting or opposing gun restrictions. Responding to Wednesday's results, Murphy said: "There's going to be a price to be paid for senators who voted the wrong way."

Gov. Dannel P. Malloy, who has met with Obama and Biden about state and federal gun control efforts, said Wednesday: "When the Senate cannot come together on an issue that is supported by the vast majority of Americans, there is little to no hope that common sense will prevail. The members who voted against this proposal should be ashamed of themselves."

Delivering the weekly White House address in place of President Barack Obama, the mother of a child killed in the Sandy Hook Elementary School shootings said the nation needs new gun laws "before our tragedy becomes your tragedy."